Before I updated to oXygen 12.2, I was able validate against a URL with a query string that generates an RNC schema ( the URL points to a PHP script that generates an RNC schema customized to the parameters in the query string). Now with the new <?xml-model?> tag, it does not recognize the URL, and gives an error message "SystemID: C:\Documents and Settings\All Users\Documents\RuleML\WP1\schema\tests\validation_on_URL_w_query_string\test_validation_on_URL_w_query_string.xml Main validation file: C:\Documents and Settings\All Users\Documents\RuleML\WP1\schema\tests\validation_on_URL_w_query_string\test_validation_on_URL_w_query_string.xml Engine name: oXygen Severity: error Description: There is no schema or DTD associated with the document. You can create an association either with the Associate Schema action or configuring in the Options the Preferences/Document Type Association list, or by creating a Validation Scenario. " I can (and you can too ;) manually verify that the URL is not broken, and does indeed point to an RNC schema. Also, when I use a redirect (on my server) that disguises this URL as a physical file with an .rnc extension, oXygen is able to validate against that. Below is the instance document that should validate. <?xml version="1.0" encoding="UTF-8"?> <?xml-model href="http://ruleml.org/0.91/relaxng/schema_rnc.php?backbone=x3f&default=x7&termseq=x7&lng=x1&propo=x3f&implies=x7&terms=xf3f&quant=x7&expr=xf&serial=xf" type="application/relax-ng-compact-syntax"?> <RuleML xmlns="http://www.ruleml.org/0.91/xsd"> <Assert> <Exists> <Var>X</Var> <And> <Atom> <oid> <Var>X</Var> </oid> <Rel>P</Rel> </Atom> </And> </Exists> </Assert> </RuleML> The URL redirect that does validate is "http://www.ruleml.org/0.91/relaxng/naffologeq_relaxed.rnc" Could you please modify this feature so that the explicit .rnc extension is not required? There is no need for it to be required, as the schema type is specified with the @type attribute. I would report this as an issue, but I can't find the issue tracker from your website. Tara